The correct sequence is c - a - b – d.
Soil formation occurs, grasses establish themselves in the
community, shrubs establish themselves in the community and trees establish
themselves in the community.
Secondary succession refers to the changes in
vegetation of an ecosystem after all or portion has been destroyed due to
natural or manmade effect such as wildfires or human alterations. Secondary
succession is a much more rapid process than primary succession because the
soil and nutrients are already available. Examples of secondary succession
include the renewal of a forest after a fire and the renewal of a crop after
harvesting
